Surgical stapling device with resettable anvil assembly

ABSTRACT

A surgical stapler includes an anvil assembly including an anvil head assembly pivotally secured to an anvil center rod. The anvil head assembly includes a housing having a post and a cut ring assembly supported about the post and movable between retracted and advanced positions. A cut ring retainer is positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position. In its retracted position, the cut ring retainer can be received in a retainer slot formed about the post. The cut ring retainer can be ring shaped and/or formed of a resilient material to facilitate movement of the cut ring retainer into and out of the retainer slot.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/449,704 filed Jan. 24, 2017, the entire disclosure of which is incorporated by reference herein.

BACKGROUND 1. Technical Description

The present disclosure is directed to surgical stapling devices with tiltable anvil assemblies and, more particularly, to circular stapling devices with tiltable anvil assemblies that are configured for reuse.

2. Background of Related Art

Circular stapling devices for performing surgical procedures such as anastomoses, hemorrhoidectomies, and mucosectomies are well known. These devices include an anvil assembly having a center rod and an anvil head supported on the center rod. Typically, during a surgical procedure performed with a circular stapling device, the tool assembly of the stapling device is inserted into a tubular section or sections of tissue to join the tissue sections or remove diseased or damaged tissue from within the tissue section. In order to minimize trauma to the tissue section, the anvil head may be pivotally supported on the center rod to reduce the profile of the anvil head during insertion and/or removal of the tool assembly from the tissue section. In some stapling devices, a component is fractured during firing of the stapling device to facilitate tilting of the anvil head.

Due to the rising costs associated with medical procedures, reusable surgical instrumentation is desirable. Thus, a circular stapling device including a reusable or resettable anvil assembly is desirable.

SUMMARY

In one aspect of this disclosure, a surgical stapling device includes a handle assembly, an adaptor assembly, and a tool assembly. The adaptor assembly has a proximal portion coupled to the handle assembly, a distal portion, and an anvil retainer. The anvil retainer extends from the distal portion of the adaptor assembly and is movable from a retracted position to an advanced position. A tool assembly is supported on the distal portion of the adaptor assembly and includes a shell assembly and an anvil assembly. The shell assembly includes an annular staple cartridge having a plurality staples. The anvil assembly includes a center rod assembly and an anvil head assembly. The center rod assembly includes an anvil center rod defining a longitudinal axis having a proximal portion and a distal portion. The proximal portion is configured to releasably engage the anvil retainer of the adaptor assembly.

The anvil head assembly is pivotally secured to the distal portion of the anvil center rod and includes a housing and a cut ring assembly. The housing defines a recess and includes a post centrally disposed within the recess and an annular tissue contact surface positioned about the recess. The post defines a longitudinal axis and the tissue contact surface defines a plurality of staple deforming pockets. The cut ring assembly is movably supported about the post between a retracted position and an advanced position. A cut ring retainer is positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position. The anvil head assembly is pivotal from an operative position in which the longitudinal axis of the anvil center rod is aligned with the longitudinal axis of the post to a tilted position in which the longitudinal axis of the anvil center rod and the longitudinal axis of the post define an acute angle. In its retracted position, the cut ring assembly is positioned to engage the center rod to retain the anvil head assembly in the operative position and in its advanced position, the cut ring assembly is positioned to permit pivotal movement of the anvil head assembly to the tilted position.

In another aspect of the disclosure, a pivotal anvil assembly includes a center rod assembly and an anvil head assembly. The center rod assembly includes an anvil center rod defining a longitudinal axis, a proximal portion, and a distal portion. The anvil head assembly is pivotally secured to the distal portion of the anvil center rod and includes a housing and a cut ring assembly. The housing defines a recess and includes a post centrally disposed within the recess and an annular tissue contact surface positioned about the recess. The post defines a longitudinal axis. The cut ring assembly is supported about the post and movable between a retracted position and an advanced position. A cut ring retainer is positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position. The anvil head assembly is pivotal from an operative position in which the longitudinal axis of the anvil center rod is aligned with the longitudinal axis of the post to a tilted position in which the longitudinal axis of the anvil center rod and the longitudinal axis of the post define an acute angle. In its retracted position, the cut ring assembly is positioned to engage the center rod to retain the anvil head assembly in the operative position. In its advanced position, the cut ring assembly is positioned to permit pivotal movement of the anvil head assembly to the tilted position.

In embodiments, the housing of the anvil head assembly includes a distal face defining at least one reset hole. The at least one reset hole communicates with the recess and is configured to provide access to the recess to facilitate movement of the cut ring retainer from its advanced position back to its retracted position.

In some embodiments, the post defines a retainer slot having an annular configuration and the cut ring retainer is positioned within the retainer slot when the retainer is in its retracted position.

In certain embodiments, a distal end of the retainer slot includes an outwardly tapered surface that is positioned to cause expansion of the cut ring retainer as the cut ring retainer is moved from its retracted position towards its advanced position.

In embodiments, the cut ring retainer is ring shaped and is formed of a resilient material.

In some embodiments, the cut ring retainer has a spiral configuration.

In certain embodiments, the center rod assembly includes a plunger and a plunger spring that is positioned to urge the plunger towards the anvil head assembly to urge the anvil head assembly from the operative position towards the tilted position.

In embodiments, the surgical stapling device further includes a backup member that is movably supported about the post of the anvil head assembly and the cut ring assembly is supported on the backup member.

In some embodiments, the backup member defines a central opening dimensioned to receive the post and a flange positioned about the central opening, and the cut ring assembly is supported about the flange of the backup member.

In some embodiments, the cut ring assembly includes an inner sleeve and a body, wherein the inner sleeve and the body each define a central opening. The inner sleeve can be secured within the central opening of the body and the central opening of the inner sleeve can be dimensioned to receive the flange of the backup member.

In certain embodiments, the cut ring assembly includes a base member that is positioned between a proximal surface of the body and a distal surface of the backup member.

In embodiments, the backup member is formed of metal.

In some embodiments, the body is formed from a first material having a first durometer and the base member is formed of a second material having a second lower durometer.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the presently disclosed surgical stapling device with a resettable, tiltable anvil assembly are described herein below with reference to the drawings, wherein:

FIG. 1 is a side, perspective view of one embodiment of the presently disclosed surgical stapling device including a resettable, tiltable anvil assembly;

FIG. 2 is a side perspective view from a proximal end of the resettable anvil assembly shown in FIG. 1 with an anvil head of the anvil assembly in an operative position;

FIG. 3 is a perspective view from the distal end of the resettable anvil assembly shown in FIG. 2;

FIG. 4 is an exploded, side perspective view of the resettable anvil assembly shown in FIG. 2;

FIG. 5 is an enlarged view of the indicated area of detail shown in FIG. 4;

FIG. 6 is a cross-sectional view taken along section line 6-6 of FIG. 5;

FIG. 7 is a cross-sectional view taken along section line 7-7 of FIG. 5;

FIG. 8 is a perspective view from the proximal end of the anvil head of the resettable anvil assembly shown in FIG. 4;

FIG. 9 is an enlarged view of the indicated area of detail shown in FIG. 2;

FIG. 10 is side cross-sectional view through the distal end of the resettable anvil assembly shown in FIG. 1 in a pre-fired state;

FIG. 11 is side cross-sectional view through the distal end of the resettable anvil assembly shown in FIG. 1 during firing of the stapling device with the shell assembly shown in phantom as a cut ring assembly of the anvil assembly is being advanced into the anvil head;

FIG. 12 is a side perspective view of the resettable anvil assembly shown in FIG. 1 with the anvil head of the resettable anvil assembly in a tilted position;

FIG. 13 is an enlarged view of the indicated area of detail shown in FIG. 12;

FIG. 14 a cross-sectional view taken along section line 14-14 of FIG. 12;

FIG. 15 is an enlarged view of the indicated area of detail shown in FIG. 14;

FIG. 16 is a perspective view of the anvil head and retainer member of the resettable anvil assembly shown in FIG. 2 as the retainer is returned to its pre-fired position with a reset tool;

FIG. 17 is a side perspective view of an alternate embodiment of the retainer of the resettable anvil assembly shown in FIG. 4; and

FIG. 18 is a side perspective view of another alternate embodiment of the retainer member of the resettable anvil assembly shown in FIG. 4.

DETAILED DESCRIPTION OF EMBODIMENTS

The presently disclosed surgical stapling device including a resettable, tiltable anvil assembly will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician. In addition, the term clinician is used generally to refer to medical personnel including doctors, nurses, and support personnel.

The presently disclosed surgical stapling device includes a handle or actuator assembly, an elongate body or adaptor, and a tool assembly coupled to a distal portion of the adaptor. The tool assembly includes a tiltable anvil assembly and a shell assembly. The anvil assembly includes a center rod that is releasably coupled to the adaptor and an anvil head that is pivotally coupled to the center rod. The anvil head supports a cut ring assembly that is movable between a pre-fired or retracted position in which the cut ring assembly retains the anvil head in an untilted or operative position and a second or advanced position in which the cut ring assembly is positioned to allow movement of the anvil head to a tilted position. The anvil assembly also includes a retainer that is movable from a pre-fired or retracted position within the anvil head to an advanced position within the anvil head to allow the cut ring assembly to move from the first position to the second position. In embodiments, the anvil head defines at least one reset hole that is dimensioned to provide access to the cut ring retainer and the cut ring assembly within the anvil head to allow the cut ring assembly and the cut ring retainer be returned to their pre-fired or retracted positions after the stapling device has been fired to return and retain the anvil head in the operative position.

Referring to FIG. 1, the presently disclosed surgical stapling device is shown generally as stapling device 10 and includes a handle or actuator assembly 20, an elongate body or adaptor assembly 30, and a tool assembly 40. The handle assembly 20 as illustrated is an electrically powered assembly and includes a grip 22 and actuation buttons 24 that can be depressed to actuate various functions of the stapling device 10 including approximation of the tool assembly and firing of staples. In embodiments, the grip 22 supports a battery pack (not shown) which powers the handle assembly 20.

In embodiments, the adaptor assembly 30 is releasably coupled to a distal portion of the handle assembly 20 and includes a plurality of drive mechanisms (not shown) that translate power from the handle assembly 20 to the tool assembly 40 in response to actuation of the actuation buttons 24 to effect operation, i.e., approximation and firing, of the tool assembly 40. The adaptor assembly 30 also includes an anvil retainer 59 that extends from a distal portion of the adaptor assembly 30 and is movable between retracted and advanced positions. U.S. Pat. Nos. 9,247,940, 9,055,943, and 8,806,973, and U.S. Publication No. 2015/0014392 disclose exemplary embodiments of powered handle assemblies and adaptor assemblies and are incorporated herein by reference in their entirety. Alternately, the elongate body or adaptor assembly 30 can be non-removably secured to the actuator assembly 20.

It is also envisioned that the actuator assembly 20 could be manually powered. Examples of manually powered handle assemblies are described in U.S. Pat. Nos. 8,789,737, 8,424,535 (535 patent) and U.S. Pat. No. 8,360,295 which are incorporated herein in their entirety by reference.

The tool assembly 40 includes a shell assembly 50 and an anvil assembly 60. The shell assembly 50 includes a housing 52 that supports a staple cartridge 54 having an annular array of staple pockets 56. The staple cartridge 54 has a distally facing tissue contact surface 57. Each of the staple pockets 56 houses a staple (not shown). The shell assembly 50 also includes components that facilitate firing of the staples from the staple cartridge 54 and an annular knife 58 (FIG. 11) that is movable from a retracted position recessed within the housing 52 to an advanced position extending into the anvil assembly 60. The '535 patent describes the components of a shell assembly suitable for use with the presently disclosed stapling device 10.

Referring to FIGS. 2-8, the resettable anvil assembly 60 includes an anvil center rod assembly 62 and an anvil head assembly 64 that is pivotally supported on a distal portion of the anvil center rod assembly 62. The anvil head assembly 64 includes a housing 70 including a post 72 and an anvil tissue contact surface 74, a backup member 76, a cut ring assembly 78, a cam latch member 80, and a cut ring retainer 82. In embodiments, the housing 70, the post 72, and the anvil tissue contact surface 74 are monolithically formed. Alternately, any one or all of the housing 70, post 72, and anvil tissue contact surface 74 can be formed separately and secured together using any known fastening technique including welding, crimping or the like. The housing 70 of the anvil head assembly 64 defines a recess 86 (FIG. 4) positioned between the post 72 and the tissue contact surface 74 with the post 72 centrally located within the recess 86. The tissue contact surface 74 of the housing 70 faces the tissue contact surface 57 (FIG. 1) of the staple cartridge 54 and includes a plurality of staple deforming pockets 92 for receiving and deforming staples ejected from the staple cartridge 54.

The housing 70 of the anvil head assembly 64 also defines one or more reset holes 75 (FIGS. 3 and 4) that extend through a distal face of the housing 70 and communicate with the recess 86. Although three reset holes 75 are shown in the illustrated embodiment, the housing 70 may define a different number of reset holes, e.g., 2, 3, 4, 5, 6, or more reset holes. The reset holes 75 communicate with the recess 86 at a position adjacent an outer surface of the post 72 (FIG. 5). The reset holes 75 are positioned radially inwardly of vent holes 77. The vent holes 77 allow fluid and tissue that is compressed between the staple cartridge 54 and the anvil head assembly 64 to escape from the anvil assembly 60.

With particular reference to FIG. 4, the backup member 76 defines a central opening 96 that is dimensioned to receive the post 72 of the housing 70. The central opening 96 is dimensioned to facilitate movement of the backup member 76 about the post 72 from a pre-fired, retracted position to an advanced position within the recess 86 of the housing 70 as discussed in further detail below. The backup plate 76 includes a raised flange 98 that is positioned about the opening 96. Although the raised flange 98 is illustrated as having a circular shape, other configurations are envisioned, e.g., square, rectangular, triangular, etc. The backup member 76 includes a pair of inwardly extending fingers 100 that are movable into and out of engagement with a distal portion of the center rod assembly 62 of the anvil assembly 60 to allow the anvil head assembly 64 to pivot in relation to the center rod assembly 62 as discussed in detail below. In embodiments, the backup member 76 is formed from a hard material such as metal although other materials of construction are envisioned. U.S. Pat. No. 8,540,132 which is incorporated herein in its entirety by reference discloses a tiltable anvil assembly that includes a backup member and cut ring assembly that are movably positioned about a post of an anvil head.

In embodiments, the cut ring assembly 78 includes an annular body 102 formed of a first material, an annular base member 104 formed of a second material, and an annular inner sleeve 106. The body 102, base member 104, and sleeve 106 of the cut ring assembly 78 define openings 108 a-c, respectively, that are configured to receive the flange 98 of the backup plate 76. The sleeve 106 is secured to an inner surface 102 a of the body 102 and is positioned about the flange 98 of the backup member 76 to secure the cut ring assembly 78 to the backup member 76. Thus, movement of the backup member 76 between retracted and advanced positions causes corresponding movement of the cut ring assembly 78.

In embodiments, the sleeve 106 is formed from a hard plastic material that is over molded onto the inner surface 102 a of the body 102 of the cut ring assembly 78. Alternately, the sleeve 106 can be secured to the inner surface 102 a of the body 122 using other known fastening techniques. For example, the outer wall of the sleeve 106 may include protrusions 120 that engage the inner surface 102 a of the body 102 to secure the sleeve 106 to the body 102. In embodiments, the sleeve 106 is press-fit onto the flange 98 of the backup member 76 to secure the sleeve 106 and the body 102 of the cut ring assembly 78 onto the backup member 76. The body 102 is secured to the base member 104 with an adhesive or the like such that the base member 104 is sandwiched between the body 106 and the backup member 76. The base member 104 can also be secured to the backup member 76 using an adhesive.

In embodiments, the body 102 of the cut ring assembly 78 is formed from a first material having a first durometer, e.g., polypropylene, and the base member 104 is formed of a second material having a second lower durometer e.g., polyester. The above described construction of the cut ring assembly 78 allows the knife 58 (FIG. 11) to initially pierce through the soft durometer material of the body 102, and then pierce the second lower durometer material of the base member 104, and finally to bottom out against the harder material of the backup plate 76 as discussed in detail below.

It is envisioned that a variety of cut ring assemblies can be included in the presently disclosed anvil head assembly. For example, the cut ring assembly need not include a sleeve and/or a base member 104.

Referring to FIGS. 4-10, the body 102 of the cut ring assembly 78 includes an outer wall 110 (FIG. 4) having a series of projections 112. The housing 70 of the anvil assembly 60 includes an inner wall 70 a (FIG. 7) defining an annular groove 114. In embodiments, the projections 112 of the body 102 of the anvil head assembly 64 are slidably received within the annular groove 114 (FIG. 10) to guide movement of the cut-ring assembly 78 and backup member 76 between their advanced and retracted positions within the recess 86 of the housing 70. An annular stop member 116 is formed on the housing 70 at a proximal end of the annular groove 114. The annular stop member 116 and the projections 112 of the body 102 of cut ring assembly 78 are configured to retain the cut ring assembly 78 and backup plate 76 within the recess 86 of the housing 70 of the anvil head assembly 60.

The post 72 of the anvil head assembly 64 defines an annular retainer slot 130 that receives the cut ring retainer 82. The retainer slot 130 is spaced from the distal end of the recess 86 of the housing 70 by a cylindrical portion 136 of the post 72 and includes an outwardly tapered surface 132. The outwardly tapered surface 132 extends between a base of the retainer slot 130 and cylindrical portion 136 of the post 72 such that the cylindrical portion 136 of the post 72 has a larger diameter than the base of the retainer slot 130. The cut ring retainer 82 is positioned within the retainer slot 130 and has a width that is larger than the depth of the retainer slot 130 such that the cut ring retainer 82 extends into the recess 86 to engage a proximal surface of the backup member 76 when the backup member 76 and the cut ring assembly 78 are in their pre-fired or retracted positions (FIG. 10). Engagement between the cut ring retainer 82 and the backup member 76 releasably retains the backup member 76 and the cut ring assembly 78 in their retracted positions. The outwardly tapered surface 132 defining the retainer slot 130 is positioned to expand the diameter of the cut ring retainer 82 when the cut ring retainer 82 is advanced within the recess 86 to a position about the cylindrical portion 136 of the post 72 in response to firing of the tool assembly as discussed in further detail below.

In embodiments, the cut ring retainer 82 includes a resilient ring 82 a. In embodiments, the resilient ring 82 a has a spiral configuration (FIG. 6) and is expandable upon application of a sufficient force in the distal direction. More specifically, when the resilient ring 82 a is pressed distally with a predetermined force into the outwardly tapered surface 132 defining a distal portion of the retainer slot 130, such as when the annular knife drives the cut ring assembly 78 into the recess 86 of the housing 70 of the anvil assembly 60, the diameter of the resilient ring 82 a is expanded as the resilient ring 82 a passes distally over the outwardly tapered surface 132. As this occurs, the resilient ring 82 a moves distally within the recess 86 of the housing 70 and passes out of the retainer slot 130 and onto the cylindrical portion 136 of the post 72. When the cut ring retainer 82 is advanced onto the cylindrical portion 136 of the post 72, the cut ring retainer 82 is positioned closely adjacent and/or at least partially over the reset holes 75.

It is envisioned that the cut ring retainer 82 can have a variety of alternative configurations. For example, a cut ring retainer 182 shown in FIG. 17 can have a substantially cylindrical configuration with areas 184 of increased width that are dimensioned to extend radially outwardly from within the retainer slot 130 into engagement with a proximal surface of the backup member 76. The areas 184 of increased width may vary in size and shape. In addition, the retainer 182 may define a split 186 that allows the diameter of the retainer 182 to expand along the outwardly tapered surface 132 defining the retainer slot 130 and onto the cylindrical portion 136 of the post 72.

As shown in FIG. 18, a cut ring retainer 282 may have a series uniformly sized and shaped areas 284 of increased thickness. In addition, the retainer 282 may define a split 286 that allows the diameter of the retainer 282 to expand along the outwardly tapered surface 132 defining the retainer slot 130 and onto the cylindrical portion 136 of the post 72. Alternately, it is envisioned that the retainer 182 and/or 282 need not be split but rather may be include a resilient body that expands about the outwardly tapered surface 132 defining the retainer slot 130 to pass onto the cylindrical portion 136 of the post 72.

With reference again to FIGS. 2-4, the center rod assembly 62 includes a center rod 140, a plunger 142, and a plunger spring 144. A first end of center rod 140 includes a pair of spaced arms 146 that define a cavity 148 (FIG. 10) dimensioned to receive the post 72 of the anvil head assembly 64. Each arm 146 of the pair of arms 146 has distally facing flat 149 a and transverse through bore 150. The transverse through bores 150 define an axis that intersects a central longitudinal axis of center rod 140. Alternately, the through bore 150 axis can be offset from the longitudinal axis of center rod 62. The post 72 of anvil head assembly 64 is dimensioned to be positioned within cavity 148 defined between the spaced arms 146 of the center rod 62 and also includes a transverse through bore 152. A pivot member 154 extends through the through bores 150 of the arms 146 and the through bore 152 of the post 72 to pivotally secure the post 72 to the center rod 140 such that the anvil head assembly 64 is pivotally mounted to the center rod assembly 62 between an operative position (FIG. 2) and a tilted position (FIG. 12). The distally facing flats 149 a formed on the distal end of the center rod 140 are dimensioned to support the inwardly extending fingers 100 of the backup member 76 when the backup member 76 is in the retracted position within the recess 86 of the housing 70 to releasably retain the anvil head assembly 64 in the operative position as discussed in further detail below.

The cam latch member 80 is received in a cutout 172 (FIG. 8) defined within the post 72 of the anvil head assembly. The cam latch member 80 defines a through bore 170 (FIG. 4) that receives the pivot member 154 such that the cam latch member 80 is pivotally supported about the pivot member 154 within the cutout 172. The plunger 142 is urged by the plunger spring 144 into engagement with the cam latch member 80 and a proximal end of the post 72 of the anvil head assembly 64 to urge the anvil head assembly 64 about the pivot member 154 towards the tilted position (FIG. 12). The cam latch member 80 is configured to engage the inner surface of the backup member 76 to prevent movement of the backup member 76 and, thus, the cut ring assembly 78 from the advanced position back to the retracted position after the stapling device 10 is fired.

For a more detailed description of anvil assembly 60 including operation of the cam latch member 80, the plunger 142, and the plunger spring 144, please refer to the U.S. Pat. No. 8,540,132 (“the '132 patent”), the content of which is incorporated herein by reference in its entirety.

Referring to FIGS. 9 and 10, prior to firing of the stapling device 10 (FIG. 1), the backup member 76 and the cut ring assembly 78 are in their retracted positions with the cut ring assembly 78 supported about the flange 98 of the backup member 76. The cut ring retainer 82 is positioned within the retainer slot 130 and extends outwardly into the recess 86 to a position distally of the backup member 76 to retain the backup member 76 in its retracted position.

With the backup member 76 in its retracted position, the inwardly extending fingers 100 of the backup member 76 are supported on the distally facing flats 149 a (FIG. 9) of the center rod 140 such that the anvil head assembly 64 is retained in the operative position. As discussed above, the plunger 142 of the center rod assembly 62 is positioned to urge the cam latch member 80 and the anvil head assembly 62 about the pivot member 154 towards the tilted position (FIG. 12).

Referring to FIGS. 11-16, when the stapling device 10 (FIG. 1) is approximated and subsequently fired, the annular knife 58 (FIG. 11) of the shell assembly 50 is advanced from a retracted position recessed within the housing 52 of the shell assembly 50 to an advanced position extending into the cut ring assembly 78 of the anvil head assembly 64. As the annular knife 58 engages the cut ring assembly 78, the cut ring assembly 78 and the backup member 76 are advanced from their retracted positions to their advanced positions within the recess 86 of the housing 70 of the anvil head assembly 64. As the backup member 76 moves towards its advanced position, the backup member 76 engages the cut ring retainer 82 and advances the cut ring retainer 82, in the direction indicated by arrow “A” in FIG. 11, from a position received within the retainer slot 130, along the outwardly tapered surface 132 defining the retainer slot 130, to a position located about the cylindrical portion 136 of the post 72. As discussed above, as the retainer 82 moves distally along the outwardly tapered surface 132 in the direction indicated by arrow “B” in FIG. 11, the diameter of the cut ring retainer 82 is expanded until the cut ring retainer 82 is received about the cylindrical portion 136 of the post 72 (FIG. 14). The resilience of the cut ring retainer 82 retains the cut ring retainer 82 in an advanced position about the cylindrical portion 136 of the post 72. In this position, the cut ring retainer 82 is positioned closely adjacent to and/or at least partially over the reset holes 75 (FIG. 16).

As discussed above, when the backup member 76 moves to its advanced position, the inwardly extending fingers 100 are moved to a position spaced from the distally facing flats 149 a (FIG. 11) on the distal end of the center rod 140. When the fingers 100 are spaced from the distally facing flats 149 a and the stapling device 10 is moved to the spaced or unapproximated position in relation to the shell assembly 50, the plunger spring 144 (FIG. 4) urges the plunger 142 into the cam latch member 80 and post 72 to urge the anvil head assembly 64 towards the tilted position.

Referring to FIG. 16, after the stapling device 10 (FIG. 1) has been fired, the anvil head assembly 64 has moved to the tilted position, and the tool assembly 40 has been withdrawn from a patient's body, the anvil head assembly 64 can be manually reset to the operative position (FIG. 2). More specifically, the anvil head assembly 64 can be manually reset to the operative position by manually returning the anvil head assembly 64 against the bias of spring 144 to the operative position and inserting a reset tool 180 through the reset openings 75 of the housing 70 of the anvil head assembly 64 to return the retainer 82 and the backup member 76 to their retracted positions. When the reset tool 180 is inserted through one or more of the reset openings 75, the reset tool 180 can be manipulated to push the cut ring retainer 82 proximally within the recess 86 from its advanced position located about the cylindrical portion 136 of the post 72 back towards its retracted position. As the cut ring retainer 82 is moved towards its retracted position located within the recess 86 of the housing 70, the cut ring retainer 82 engages the backup member 76 to urge the backup member 76 and the cut ring assembly 78 supported on the backup member 76 towards their retracted positions. In the retracted position of the cut ring retainer 82, the cut ring retainer 82 is received within the retainer slot 132 and engages the backup member 76 in a position in which fingers 100 are engaged with flats 149 a of center rod 140 to retain the anvil head assembly 64 in the operative position.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

What is claimed is:
 1. A surgical stapling device comprising: a handle assembly; an adaptor assembly having a proximal portion coupled to the handle assembly, a distal portion, and an anvil retainer, the anvil retainer extending from the distal portion of the adaptor assembly and being movable from a retracted position to an advanced position; and a tool assembly supported on the distal portion of the adaptor assembly, the tool assembly including a shell assembly having an annular staple cartridge having a plurality staples and an anvil assembly, the anvil assembly including: a center rod assembly including an anvil center rod defining a longitudinal axis and having a proximal portion configured to releasably engage the anvil retainer of the adaptor assembly and a distal portion; and an anvil head assembly pivotally secured to the distal portion of the anvil center rod, the anvil head assembly including a housing and a cut ring assembly, the housing defining a recess and including a post centrally disposed within the recess and an annular tissue contact surface positioned about the recess, the post defining a longitudinal axis, the tissue contact surface of the housing defining a plurality of staple deforming pockets, the cut ring assembly being supported about the post and movable between retracted and advanced positions, and a cut ring retainer formed of a resilient material, the cut ring retainer positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position, the anvil head assembly being pivotal from an operative position in which the longitudinal axis of the anvil center rod is aligned with the longitudinal axis of the post to a tilted position in which the longitudinal axis of the anvil center rod and the longitudinal axis of the post define an acute angle, wherein in its retracted position, the cut ring assembly is positioned to engage the center rod to retain the anvil head assembly in the operative position and in its advanced position, the cut ring assembly is positioned to permit pivotal movement of the anvil head assembly to the tilted position, wherein the cut ring retainer is movable from its advanced position back to its retracted position to retain the cut ring assembly back in its retracted position.
 2. The surgical stapling device of claim 1, wherein the housing of the anvil head assembly includes a distal face defining at least one reset hole, the at least one reset hole communicating with the recess and being configured to provide access to the recess to facilitate movement of the cut ring retainer from its advanced position back to its retracted position.
 3. The surgical stapling device of claim 1, wherein the post defines a retainer slot having an annular configuration, the cut ring retainer being positioned within the retainer slot when the cut ring retainer is in its retracted position.
 4. The surgical stapling device of claim 3, wherein a distal end of the retainer slot includes an outwardly tapered surface, the outwardly tapered surface being positioned to cause expansion of the cut ring retainer as the cut ring retainer is moved from its retracted position towards its advanced position.
 5. The surgical stapling device of claim 4, wherein the cut ring retainer is ring shaped and is formed of a resilient material.
 6. The surgical stapling device of claim 4, wherein the cut ring retainer has a spiral configuration.
 7. The surgical stapling device of claim 1, wherein the center rod assembly includes a plunger and a plunger spring, the plunger spring being positioned to urge the plunger towards the anvil head assembly to urge the anvil head assembly from the operative position towards the tilted position.
 8. The surgical stapling device of claim 1, further including a backup member that is movably supported about the post of the anvil head assembly, the cut ring assembly being supported on the backup member.
 9. The surgical stapling device of claim 8, wherein the backup member defines a central opening dimensioned to receive the post and includes a flange positioned about the central opening, the cut ring assembly being supported about the flange of the backup member.
 10. The surgical stapling device of claim 9, wherein the cut ring assembly includes an inner sleeve and a body, the inner sleeve and the body each defining a central opening, the inner sleeve being secured within the central opening of the body, wherein the central opening of the inner sleeve is dimensioned to receive the flange of the backup member.
 11. The surgical stapling device of claim 10, wherein the cut ring assembly includes a base member that is positioned between a proximal surface of the body and a distal surface of the backup member.
 12. The surgical stapling device of claim 11, wherein the backup member is formed of metal.
 13. The surgical stapling device of claim 11, wherein the body is formed from a first material having a first durometer and the base member is formed of a second material having a second lower durometer.
 14. A pivotal anvil assembly comprising: a center rod assembly including an anvil center rod defining a longitudinal axis and having a proximal portion and a distal portion; and an anvil head assembly pivotally secured to the distal portion of the anvil center rod, the anvil head assembly including a housing and a cut ring assembly, the housing defining a recess and including a post centrally disposed within the recess and an annular tissue contact surface positioned about the recess, the post defining a longitudinal axis, the cut ring assembly being supported about the post and movable between retracted and advanced positions, and a cut ring retainer formed of a resilient material, the cut ring retainer positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position, the anvil head assembly being pivotal from an operative position in which the longitudinal axis of the anvil center rod is aligned with the longitudinal axis of the post to a tilted position in which the longitudinal axis of the anvil center rod and the longitudinal axis of the post define an acute angle, wherein in its retracted position, the cut ring assembly is positioned to engage the center rod to retain the anvil head assembly in the operative position, the cut ring assembly is positioned to facilitate pivotal movement of the anvil head assembly to the tilted position, wherein the cut ring retainer is movable from its advanced position back to its retracted position to retain the cut ring assembly back in its retracted position.
 15. The surgical stapling device of claim 14, wherein the housing of the anvil head assembly includes a distal face defining at least one reset hole, the at least one reset hole communicating with the recess and being configured to provide access to the recess to facilitate movement of the cut ring retainer from its advanced position back to its retracted position.
 16. The surgical stapling device of claim 14, wherein the cut ring retainer is ring shaped and is formed of a resilient material.
 17. The surgical stapling device of claim 14, wherein the cut ring retainer has a spiral configuration.
 18. The surgical stapling device of claim 14, wherein the center rod assembly includes a plunger and a plunger spring, the plunger spring being positioned to urge the plunger towards the anvil head assembly to urge the anvil head assembly from the operative position towards the tilted position.
 19. The surgical stapling device of claim 14, further including a backup member that is movably supported about the post of the anvil head assembly, the cut ring assembly being supported on the backup member.
 20. The surgical stapling device of claim 19, wherein the backup member defines a central opening dimensioned to receive the post and includes a flange positioned about the central opening, the cut ring assembly being supported about the flange of the backup member.
 21. The surgical stapling device of claim 20, wherein the cut ring assembly includes an inner sleeve and a body, the inner sleeve being secured within a central opening of the body and configured to receive the flange of the backup member.
 22. The surgical stapling device of claim 21, wherein the cut ring assembly includes a base member that is positioned between a proximal surface of the body and a distal surface of the backup member.
 23. The surgical stapling device of claim 22, wherein the backup member is formed of metal.
 24. The surgical stapling device of claim 23, wherein the body is formed from a first material having a first durometer and the base member is formed of a second material having a second lower durometer.
 25. A pivotal anvil assembly comprising: a center rod assembly including an anvil center rod defining a longitudinal axis and having a proximal portion and a distal portion; and an anvil head assembly pivotally secured to the distal portion of the anvil center rod, the anvil head assembly including a housing and a cut ring assembly, the housing defining a recess and including a post centrally disposed within the recess and an annular tissue contact surface positioned about the recess, the post defining a longitudinal axis, the cut ring assembly being supported about the post and movable between retracted and advanced positions, and a cut ring retainer formed of a resilient material, the cut ring retainer positioned about the post and movable between a retracted position in which the cut ring retainer retains the cut ring assembly in its retracted position and an advanced position to permit movement of the cut ring assembly to its advanced position, the anvil head assembly being pivotal from an operative position in which the longitudinal axis of the anvil center rod is aligned with the longitudinal axis of the post to a tilted position in which the longitudinal axis of the anvil center rod and the longitudinal axis of the post define an acute angle, wherein in its retracted position, the cut ring assembly is positioned to engage the center rod to retain the anvil head assembly in the operative position, the cut ring assembly is positioned to facilitate pivotal movement of the anvil head assembly to the tilted position; wherein the post defines a retainer slot having an annular configuration, the cut ring retainer being positioned within the retainer slot when the cut ring retainer is in its retracted position.
 26. The surgical stapling device of claim 25, wherein a distal end of the retainer slot includes an outwardly tapered surface, the outwardly tapered surface being positioned to cause expansion of the cut ring retainer as the cut ring retainer is moved from its retracted position towards its advanced position. 